Group theory, is my solution correct?

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Homework Statement



if H is a normal subgroup of G and has index n, show that g^n is in H for all g in G.



The Attempt at a Solution



Take H a normal subgroup of a group G. Take g in G.

Consider gH in the quotient group G/H. Because |G/H| = [G:H] = n, (gH)^n = eH.

But g^nH = (gH)^n = eH. Thus g^n is in H.


please tell me if this is right or what i need to add,, thanks for your help!
 
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This is a correct proof.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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